A refrigerator is basically a box that is very cold inside. The heat inside the box is made to move outside, where it flows out into the air. This is achieved by means of a pipe that contains a fluid called a refrigerant. The refrigerant flows around the pipe, becoming a vapour and then condensing back into a liquid. As it becomes a vapour, the refrigerant takes heat from inside the refrigerator.
The refrigerant, which is now in a liquid state, passes through the expansion valve and turns into a cool gas due to the sudden drop in pressure. As the cool refrigerant gas flows through the chiller cabinet, it absorbs the heat from the food items inside the fridge. The refrigerant, which is now a gas, flows into the compressor, which sucks it inside and compresses the molecules together to make it into a hot, high-pressure gas.
Now, this gas transports to the condenser coils (thin radiator pipes) located at the back of the fridge, where the coils help dissipate its heat so that it becomes cool enough to condense and convert back into its liquid phase. Because the heat collected from the food items is given off to the surroundings via the condenser, it feels hot to the touch.
After the condenser, the liquid refrigerant travels back to the expansion valve, where it experiences a pressure drop and once again becomes a cool gas. It then absorbs heat from the contents of the fridge and the whole cycle repeats itself.
Parts of a refrigerator
A refrigerator consists of a few key components that play a vital role in the refrigeration process:
Expansion valve
Also referred to as the flow control device, an expansion valve controls the flow of the liquid refrigerant (also known as ‘coolant’) into the evaporator. It’s actually a very small device that is sensitive to temperature changes of the refrigerant.
Compressor
The compressor consists of a motor that ‘sucks in’ the refrigerant from the evaporator and compresses it in a cylinder to make a hot, high-pressure gas.
Evaporator
This is the part that actually cools the stuff kept inside a refrigerator. It consists of finned tubes (made of metals with high thermal conductivity to maximize heat transfer) that absorb heat blown through a coil by a fan. The evaporator absorbs heat from the stuff kept inside, and as a result of this heat, the liquid refrigerant turns into vapor.
Condenser
The condenser consists of a coiled set of tubes with external fins and is located at the rear of the refrigerator. It helps in the liquefaction of the gaseous refrigerant by absorbing its heat and subsequently expelling it to the surroundings. As the heat of the refrigerant is removed, its temperature drops to condensation temperature, and it changes its state from vapor to liquid.